1. Field of the Invention
The present invention relates to a process monitoring system which backs up the running of a plant by the use of a computer and a display device. Also, it relates to a window displaying method which offers display picture frames well suited to monitoring and operations.
2. Description of the Related Art
A process monitoring and control system for monitoring and controlling the installations of a plant generally comprises a display device such as a CRT, and an operation input terminal such as a touch panel, light pen or mouse, capable of giving operation inputs on the display screen of the device, in order to integrate the information of the plant and to enhance the operability of the plant.
Run monitoring picture frames to be displayed on the display device are in the number of several tens in a small scale plant, and can even reach the number of several hundred in a large scale plant.
In the case of a system furnished with a plurality of CRTs, the operator of the plant monitors the runs of the plant with necessary frames displayed in parallel. However, in a case where only one CRT is disposed or where the number of CRTs is insufficient for the frames desired to be displayed, the operator must changeover the display frames frequently.
In recent years, the techniques of divisional frame display, window display, etc. have been adopted as methods for integrally displaying information items on a single frame.
As can be seen from, for example, a plant monitoring system as described in Japanese Patent Application Laid open No. 177511/1986, the window display is such that an alarm frame or a guidance frame is displayed in superimposed relation on a plant monitoring frame, and the operator of a plant commands the system to display, erase and move windows by the use of a keyboard, a mouse or the like, thereby obtaining the optimum display frame. Further, although not directly relevant to plants, a technique which concerns the enlargement, reduction and display position alteration of a window is disclosed in Japanese Patent Application Laid-open No. 250129/1989, and a technique according to which, in the case of displaying a plurality of windows in succession, an empty area capable of window display on a frame without overlapping any of the existent window areas is ascertained so as to set a new window in the empty area, is disclosed in Japanese Patent Application Laid open No. 250130/1989.
The prior art method for monitoring a plurality of frames without using the window display, has the problem that the operations of changing over the frames are troublesome in the case of a single an insufficient numbers of CRTs.
Besides, with the prior:art method wherein, when the window is to be displayed on the single frame, the display position (coordinates) of the window and the size thereof are fixed, so in order to observe information in an undisplayed portion of the window, the window must either be moved and displayed, or erased and then redisplayed by the use of a the mouse or the like. This similarly incurs the problem of troublesome operations. Further, the prior-art method wherein an empty area not overlapping any of the existent window areas is ascertained in order to avoid an overlap of the windows cannot be directly applied to the monitoring of the running of a plant. The reason for this is as follows: The monitoring frame, or the like, of the plant is displayed on the whole screen, and it is considered as one existent window. Accordingly, the empty area which avoids the overlap of the windows when displaying the new window does not originally exist, and the new window is inevitably displayed superimposed on the monitoring frame or the like.
Meanwhile, as another prior-art technique, Japanese Patent Application Laid-open No. 46516/1988 or No. 94483/1986 discloses a process monitoring system wherein the monitoring image of plant installations or the like picked up by an industrial television camera is digitized and processed and wherein the digital image is displayed on a display device simultaneously with the monitoring data of a object process to be controlled.
The prior-art technique refers to the fact that the monitoring control information items and the video information of the installations or the like, which are relevant to each other, are simultaneously displayed, or the fact that a frame in computer graphics is automatically displayed upon the generation of an abnormal signal in a plant. However, it does not take into consideration the monitoring and handling capabilities of the system for an operator who actually monitors and handles the system on and through the display device. This poses a problem as to a man machine interface. More specifically, the technique leaves room for improvement in the man-machine interface regarding, for example, how a device to be operated is selected and acknowledged, how the corresponding relation between the image and the device is acknowledged, and when and how each image is selected.